Guides

How to add signatures and stamps to a PDF, how to clean up a scanned image, and how to handle documents safely.

• How to add an image to a PDFHow to place a PNG or JPG onto a PDF page, size it correctly and export a new file — including the mistakes people hit most often.
• Handling contract PDFs safelyContract PDFs carry more than their visible text. A practical guide to metadata, failed redaction, passwords vs. encryption, and image stamps.
• Keeping image quality when you add it to a PDFWhy images look blurry in a PDF, how pixels-per-inch at final size really works, and the quick check that tells you if an image is big enough.
• What happens to your file when you use an online PDF toolWhere does your document go when you upload it to a free PDF tool? Server-side vs. browser-side processing, and how to check which one a tool uses.
• How to add a stamp to a PDFPlace a signature, company seal, or stamp image onto a PDF page and save a new file, with practical guidance on sizing, placement, and legal limits.
• How to remove the white background from a scanned stampWhy scanned signatures and seals arrive with a white box, how transparency removal actually works, and the three things that usually make it fail.
• How to scan a stamp or signature cleanlyResolution, paper, pen choice and scanner settings that produce a signature or seal scan clean enough to reuse in PDFs for years.
• How to sign a PDF on your phoneAdd a signature image to a PDF using only your phone: capturing a clean signature, getting the file out of email, and finding the result afterwards.
• Digital signatures vs. signature images: what's the differencePasting a signature image onto a PDF and applying a cryptographic digital signature are entirely different things. Here is how each actually works.
• How to make a PNG with a transparent backgroundWhat transparency actually is, why JPG can never have it, PNG-8 versus PNG-24 alpha, and why off-white backgrounds are so hard to remove cleanly.